线段树入门

http://ac.jobdu.com/problem.php?pid=1544
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

const int Maxint = 0x7fffffff;
const int Max = 200010;

int node[Max];
int data[Max];

void createSegTree(int L, int R, int root)
{
	if (L == R)
	{
		node[root] = data[L];
		return ;
	}
	int mid = (L + R) / 2;
	createSegTree(L, mid, root * 2 );
	createSegTree(mid + 1, R, root * 2 + 1);
	if (node[root] > node[root * 2])
		node[root] = node[root * 2];
	if (node[root] > node[root * 2 + 1])
		node[root] = node[root * 2 + 1];
}

int query(int qL, int qR, int L, int R, int root)
{
	if (L > qR || R < qL) return Maxint;
	if (qL <= L && R <= qR)
		return node[root];
	int mid = (L + R) / 2;
	int Lmin = query(qL, qR, L, mid, root * 2);
	int Rmin = query(qL, qR, mid + 1, R, root * 2 + 1);
	return Lmin < Rmin ? Lmin : Rmin;
}

void setNode(int n)
{
	for (int i = 1; i <= n; ++i)
		node[i] = Maxint;
}

int main()
{
	//freopen("in.txt", "r", stdin);
	//freopen("out.txt", "w", stdout);
	int n, t, qL, qR;
	while(scanf("%d", &n) != EOF)
	{
		setNode(2 * n + 1);
		for (int i = 1; i <= n; ++i)
			scanf("%d", &data[i]);
		createSegTree(1, n, 1);
		//for (int i = 1; i <= 2 * n + 1; ++i)
		     //printf("%d ", node[i]); printf("\n");
		scanf("%d", &t);
		while(t)
		{
			--t;
			scanf("%d %d", &qL, &qR);
			if (qL == qR) printf("%d\n", data[qL]);
			else printf("%d\n", query(qL, qR, 1, n, 1));
		}
	}
	return 0;
}